linux-kernel - Re: [PATCH 10/13] x86: Move cond resched for copy_{from,to}

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Message-ID: <CAHGf_=p-HKz7FZ9cW7k+_64G2e+YtqaYc7mgK1ZvZoHjae+ABw@mail.gmail.com>
Date:	Tue, 20 Aug 2013 17:03:14 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 10/13] x86: Move cond resched for copy_{from,to}_user into
 low level code 64bit

>> Hmm. I can do that, but wouldn't that make CONFIG_PREEMPT_VOLUNTARY
>> mostly equivalent to CONFIG_PREEMPT_NONE?
>
> According the the Kconfig help, PREEMPT_VOLUNTARY is about the
> *explicit* preemption points. And we do have a lot of them in
> "might_sleep()".
>
> And personally, I think it makes a *lot* more sense to have a
> "might_sleep()" in the MM allocators than it does to have it in
> copy_from_user().

AFAIK, MM allocation already does that.

struct page *
__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, nodemask_t *nodemask)
{
(snip)
   might_sleep_if(gfp_mask & __GFP_WAIT);


btw, Sorry for the very late response. I haven't noticed this thread.
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